As wells have grown more complex in North American shale plays, challenging wellbore conditions, increasingly complicated lithologies and faster drilling have made it necessary to advance shale shaker technology. Shakers must be designed to maximize solids removal and thereby ensure the consistency and reliable operation and performance of the drilling fluid. This results in a fluid that requires less costly dilution to optimize both drilling performance and wellbore condition. National Oilwell Varco (NOV) developed the Brandt SABRE modular shale shaker to provide the industry with improved shaker performance and reliability.
Designed for a changing market
The SABRE shale shaker system is based on a scalable platform that can be easily changed from a single-deck to a double-deck unit and from a double-deck to a triple-deck unit. The ability to make this upgrade in the field eliminates the need to change out the complete shaker system to gain increased capacity. The design also provides distinct advantages. For example, mounting the drive assemblies directly over the side walls of the basket ensures better energy transfer to the screens. The gravitational force is set at 7G, with the counterweights adjustable to compensate for increasing the number of decks.
The system provides increased fluids-handling capacity and the ability to deliver drying cuttings. Being able to handle 1.5 to two times more fluids than comparable high-performance shakers enables better control of low-gravity solids throughout the entire drilling process by the system, thereby reducing dilution and associated logistics costs. Its ability to generate dryer cuttings than conventional equipment also results in a reduction in haul-off/disposal costs. Secondly, for operators whose drilling application requires the retention and recovery of costly lost circulation material or wellbore stabilization materials, SABRE’s triple-deck configuration can be set up to retain these particles and reintroduce them into the fluid system while still removing the undesirable low-gravity solids.
Performance was not the only factor in designing a new shaker system; improved safety, ease of use and durability also were critical design considerations. The lightweight screens used by the shaker system weigh 14 lb and can be easily changed by a single operator from the front of the shaker in a matter of minutes.
A major operator installed a single SABRE shaker based off promising early results from R&D testing. The operator’s main objective was to obtain relevant performance data in real drilling conditions to determine if the new shaker system was viable as a replacement for other shakers as part of a larger installation. The rig that the SABRE system was run on had high-performance single-deck shakers to offer an appropriate comparison. All aspects of the SABRE system, from installation through to operation, were documented, beginning with the retrofit installation of a single SABRE shake into the rig’s existing shaker skid.
An immediate benefit was that the shaker could be installed onto the skid without need for modification, providing the operator and contractor with the flexibility of implementing the new shaker into operation with minimal downtime and cost. Furthermore, it allowed use of the skid’s existing flow distribution system. Installation of the SABRE was completed in less than 8 hours, which could easily be decreased on subsequent shakers. It also demonstrated that a complete retrofit could be achieved within a 24-hour period or during a rig move.
The shaker system handled 70% to 100% of the total flow (±600 gpm) throughout the five-well program with American Petroleum Institute (API) 200 mesh screens
fitted. On this test, screens ranged from API 140 mesh through API 230 mesh during the 8½-in. oil based mud sections, and the ROP averaged 18.2 m/hr to 33.5 m/ hr (60 ft/hr to 110 ft/hr). SABRE consistently discharged significantly dryer cuttings compared to the high-performance single-deck shakers, with retention of oil on cuttings (ROC) averaging 8.85% compared with 11.2%. This was achieved while consistently maintaining low-gravity solids levels below 11.8% with only one SABRE shaker. There was also no requirement to run any other solids control equipment (such as centrifuges) with no increase in the additional dilution typically seen on previous comparable wells. The reduction
in ROC meant that haul-off and treatment costs also were reduced.
The SABRE yielded lower overall screen usage and cost compared to the incumbent shakers. Only two shakers were used for most of the five-well trial, reducing screen usage and improving system flexibility.
In addition, since one shaker was frequently offline, screen inspections and changes could be made very easily. Throughout the program only 91 screens were used in total, which consisted of 24 SABRE screens and 67 screens for the other shaker type. This was significantly less that that seen on the five previous wells drilled with the same rig, where 250 screens had been used. The company man, mud engineers, toolpusher and rig crew all approved of the new system and verified its improved performance over their existing options, with savings of approximately $192,000 during the five-well campaign. With a complete SABRE shaker system (rather than the single test unit), these cost savings and overall benefits would have been significantly greater.
Shale operators drilling across North America and elsewhere will continue to focus on reducing costs and increasing efficiencies for the foreseeable future, particularly as markets remain volatile and shareholders call for greater capital discipline. These needs are driving improvements in solids control, with shale shakers being a primary driver in maintaining the effectiveness and the desired properties of the drilling fluids and thus holding significant value. The more capable a shale shaker, the greater the efficiencies and potential production of the wells. With Brandt SABRE, NOV has brought together design ingenuity, lower total cost of ownership and improved reliability in a modular, flexible system.
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